Gas turbine or steam turbines are used in many fields for driving generators or driven machines. In this case, the energy content of a fuel or superheated steam is used for producing a rotational movement of a turbine shaft.
To this end, in the gas turbine turbine the fuel is combusted in a combustor, wherein compressed air is supplied from an air compressor. The operating medium, which is produced in the combustor as a result of combustion of the fuel, is directed in this case under high pressure and under high temperature via a turbine unit which is connected downstream to the combustor, where it is expanded, performing work.
For producing the rotational movement of the turbine shaft, in this case a number of rotor blades, which are customarily assembled into blade groups or blade rows, are arranged on this and drive the turbine shaft via an impulse transfer from the operating medium. For flow guiding of the operating medium in the turbine unit, moreover, stator blades, which are connected to the turbine casing and assembled to form stator blade rows, are customarily arranged between adjacent rotor blade rows.
The stator blades in this case are fixed in each case on a stator blade carrier of the turbine unit or compressor unit via a blade root which is also referred to as a platform. Depending upon the design aim of the gas turbine, in this case the stator blades of the gas turbine can be fastened either on a common stator blade carrier, or for each turbine stage or compressor stage provision is made for separate axial segments which are customarily rigidly interconnected. The use of a plurality of axial segments offers the advantage that on the one hand cast parts which are smaller and therefore more favorable to produce are used, and on the other hand the materials of the individual segments can be individually adapted to the physical boundary conditions which prevail in the respective axial region.
In stationary gas turbine turbines, the stator blade carrier is furthermore customarily of conical or cylindrical form and the stator blade carrier, or its individual axial segments, consists, or consist, in each case of an upper and a lower segment which are interconnected via flanges, for example. Axial segments which are axially adjacent to each other can be interconnected in this case via a tie rod connection according to DE 190 159.
In the design of today's gas turbine turbines, in addition to the achievable power, a particularly high efficiency is customarily a design aim. An increase of the efficiency can basically be achieved in this case, for thermodynamic reasons, by an increase of the discharge temperature at which the operating medium flows out of the combustor of the gas turbine turbine and flows into the turbine unit. Therefore, temperatures of about 1200° C. to 1500° C. are aimed at, and also achieved, for such gas turbine turbines.
At such high temperatures of the operating medium, however, the components and parts which are exposed to this are exposed to high thermal loads. In the case of a stator blade carrier which is assembled from a plurality of axial segments, this leads to an axial and radial displacement of the axial segments in relation to each other on account of the current temperature profile and of the variable thermal deformation behavior of the individual axial segments. This leads to a high mechanical load of the connection between the axial segments, which can lead to a rapid material fatigue with resulting cracks or even fractures in the connecting region.